Wireless communication systems provide for radio communication links to be arranged within the system between a plurality of user terminals. Such user terminals may be mobile and may be known as ‘mobile stations’ or ‘subscriber units.’ At least one other terminal, e.g. used in conjunction with subscriber units, may be a fixed terminal, e.g. a control terminal, base station, repeater, and/or access point. Such a system typically includes a system infrastructure which generally includes a network of various fixed terminals, which are in direct radio communication with the subscriber units. Each of the base stations operating in the system may have one or more transceivers which may, for example, serve subscriber units in a given local region or area, known as a ‘cell’ or ‘site’, by radio frequency (RF) communication. The subscriber units that are in direct communication with a particular fixed terminal are said to be served by the fixed terminal. In one example, all radio communications to and from each subscriber unit within the system are made via respective serving fixed terminals. Sites of neighboring fixed terminals in a wireless communication system may be offset from one another or may be non-overlapping or partially or fully overlapping. In another example, subscriber units may operate in a direct mode (e.g., without having to pass through, and without the aid of, other infrastructure devices such as a repeater or base station).
Wireless communication systems may operate according to an industry standard protocol such as, for example, the Project 25 (P25) standard defined by the Association of Public Safety Communications Officials International (APCO), or other radio protocols, such as the TETRA standard defined by the European Telecommunication Standards Institute (ETSI), the Digital Private Mobile Radio (dPMR) standard also defined by the ETSI, the Digital Mobile Radio (DMR) standard also defined by the ETSI, an open media alliance (OMA) push to talk (PTT) over cellular (OMA-PoC) standard, a voice over IP (VoIP) standard, or a PTT over IP (PoIP) standard. Protocols such as PoC, VoIP, and PoIP are implemented over broadband RANs including third generation and fourth generation networks such as third generation partnership project (3GPP) Long Term Evolution (LTE) networks.
Communications in accordance with any one or more of these standards, or other standards, may take place over physical channels in accordance with one or more of a TDMA (time division multiple access), FDMA (frequency divisional multiple access), or CDMA (code division multiple access) protocol. Subscriber units in wireless communication systems such as those set forth above send user communicated speech and data, herein referred to collectively as ‘traffic information’, in accordance with the designated protocol.
Many so-called “public safety” wireless communication systems provide for group-based radio communications amongst a plurality of subscriber units such that one member of a designated group can transmit once and have that transmission received by all other members of the group substantially simultaneously. Groups are conventionally assigned based on function. For example, all members of a particular local police force may be assigned to a same group so that all members of the particular local police force can stay in contact with one another, while avoiding the random transmissions of radio users outside of the local police force.
Subscriber units such as push-to-talk (PTT) handsets in particular have been used for some time by emergency personnel but also have recently begun to grow in general popularity. PTT handsets contain a PTT input that enables the user to communicate with a group of users on the same channel (e.g., a particular physical or logical channel statically or dynamically assigned to a particular talkgroup, or set of associated PTT devices). The communications between the PTT handsets occur at one of a set of isolated frequencies that may be selected, at least in part, by a knob on the PTT handsets. To communicate with users on other physical or logical channels, the user manually switches the channel at the PTT handset thereby causing the transmission and reception channel to change (perhaps in conjunction with a frequency assignment by a trunked repeater).
In some situations, a particular user at a particular PTT handset may wish to move all or some of the PTT devices subscribed to a currently active talkgroup to another channel. For example, a particular user may determine that a current channel being used by the talkgroup has become too crowded or interference prone, and that further communications to the entire group of PTT devices should be moved to a new channel. In another example, the particular user may wish to have further discussions with only a subset of the PTT devices in the talkgroup, and wishes to move only a portion of the PTT devices to the new channel for further discussion, such as when the talkgroup is a police force talkgroup, and the particular user wishes to move all traffic officers to a new channel temporarily for discussions specific to the traffic officers.
Conventionally, the particular user would key-up his PTT device (by activating the PTT input such as pressing a PTT button), and announce to the group that all (or only some) PTT device users should manually change their channel to the new channel. PTT device users wishing to join the new channel would then manually operate a channel selection input (such as a channel knob) on their PTT device to move to the new channel. However, relying on voice instructions from the channel change initiating user to move to a new channel, and correct manual selection of that new channel by every other PTT device user in the talkgroup, is prone to errors and increases an amount of time required to move some or all of the desired members of the talkgroup to the new channel.
Accordingly, an improved system and method is needed for automatically maneuvering some or all members of a currently active talkgroup to a new channel, in a more automated, time efficient, and error-free manner.